Cryogenic Fuel Tank And Use Thereof In A Motor Vehicle

ABSTRACT

A cryogenic fluid tank comprising an outer envelope ( 2 ) and an inner envelope ( 1 ), wherein the space between said envelopes is occupied by a multilayered insulation structure ( 3 ) wherein the inner envelope ( 1 ) is supported on a point of articulation (A) formed by a support structure ( 6 ) coupled to the outer envelope ( 2 ) and extending into the latter, wherein the point of articulation is located above the center of gravity (G) of the inner envelope. Applications: cryogenic fuel tanks in motor vehicles.

The present invention relates to cryogenic fluid tanks, in particular for the onboard storage of liquid cryogenic fuels, of the type comprising an outer envelope and an inner envelope, the space between the inner and outer envelopes being occupied by a multilayer insulating structure.

The production of tanks with multilayer insulation presents considerable difficulties in terms of manpower cost. Automation of the manufacture of multilayer insulations remains hypothetical by reason of the many connections and piping entering and leaving the tank (filling and withdrawing liquid, withdrawing the gaseous phase, various connections, etc.) Moreover, support for the inner tank is generally obtained by means of adhesive bonding systems or relatively sophisticated struts made of non-conducting materials which, in the special case of tanks for motor vehicles, must be mechanically overdesigned in order to withstand the high level of accelerations imposed by the manufacturers. These adhesives or struts and the connecting points for pipework or conductors create discontinuities harming the satisfactory insulation of the tank and constitute large sources for the entry of heat reducing the thermal performance of the tank.

The object of the present invention is to provide a cryogenic fluid tank structure greatly reducing the above disadvantages and making it possible, in a simple and effective manner, to produce a tank with improved thermal insulation and also with improved impact resistance.

To this end, according to one feature of the invention, the inner envelope is supported on a pivot point formed by a support structure secured to the outer tank and extending into the latter, the pivot point being situated above the center of gravity of the inner tank.

According to other more particular features of the invention:

-   -   the support structure extends inside a hollow volume of the         inner tank, typically with a vertical axis,     -   the inner envelope has a generally cylindrical configuration         with a longitudinal axis,     -   the lines for transferring fluid or electrical signals         communicate with the inside of the inner envelope extending         outwards into the support structure.

The present invention also relates to the use of such a tank in a motor vehicle, for storing an energetic fluid that can be used by a vehicle, in particular for its traction.

Other features and advantages of the invention will become apparent from the following descriptions of embodiments given by way of illustration but in no way limiting, made in relation to the appended drawings, in which:

FIG. 1 is a longitudinal diagrammatic sectional view of an embodiment of a tank according to the invention;

FIG. 2 is a diagrammatic view in cross section of the tank of FIG. 1; and

FIG. 3 is a diagrammatic view in partial section of an example of a pivot zone of the tank of FIG. 1.

In FIGS. 1 and 2, a tank structure can be seen for the storage of liquid cryogenic fluid L confined in an inner envelope 1 entirely positioned inside an outer envelope 2, the interspace between the envelopes 1 and 2 being occupied by a multilayer insulating structure 3 and placed under a high vacuum.

According to one feature of the invention, the multilayer insulating structure 3 advantageously consists of alternate reflecting/interleaved layers consisting of layers of polyethylene terephthalic of the aluminized Mylar™ type and of glass fiber paper of the Dextar™ or Lydall™ type. The vacuum in the interspace between the envelopes is at a pressure that is typically below 10⁻⁴ millibar.

As can be clearly seen in FIGS. 1 and 2, the envelopes 1 and 2 have a generally cylindrical configuration with a horizontal longitudinal axis arranged coaxially in relation to each other. According to one feature of the invention, the inner envelope 1 is supported in a pivoting manner, at a point A, situated in the normal configuration in use of the tank above the center of gravity G of the envelope 1 enclosing a store of liquid L. The pivot point A is formed between the bottom 4 of a bell-shaped structure 5 extending vertically from the bottom of the inner envelope 1, to which it is secured, to the vicinity of the upper wall of the latter, and by the upper end of a tubular structure 6 extending vertically, into the bell 5 coaxially to the latter, from the bottom of the inner envelope 1 to which it is secured. In order to facilitate dismantling for inspection and maintenance, the bell-shaped structure 5 and the tubular structure 6 can be assembled to the envelopes 1 and 2 by a system of flanges as shown in FIG. 1.

As shown in FIGS. 1 and 2, all the devices for transferring fluids or electrical signals emerging inside the inner envelope 1, such as the line 7 for filling liquid into the inner envelope 1, the probe 8 for measuring the level of liquid L inside the envelope 1, or the take-off line 9 of the gas neck of the inner envelope 1, pass through the bottom walls of the bell 5 and the tubular support 6 in the vicinity of the pivot point A and extend into the tubular support 6 to the outside of the outer envelope 2, typically through a valve housing 10 enclosing the valves 11 also placed under vacuum.

It will be understood that with such an arrangement, the inner envelope 1 is suspended in a pendular manner inside the outer envelope 2, angular swinging of the inner envelope 1 about the pivot point A under the effect of external and/or internal accelerations being immediately damped by the compacted insulating structure 3 between the envelopes 1 and 2, the inner envelope automatically recovering, simply by gravity, its balanced configuration at rest in the absence of accelerations. According to the invention therefore, the inner envelope is protected against a large number of accidents, which makes it possible to simplify and automate the installation of insulation around this envelope. Moreover, the points where pipes and conductors pass through the wall are grouped together in the narrow pivot zone about the point A inside the inner envelope 1, in this way greatly reducing all thermal bridges to the outside.

In the particular embodiment shown in FIG. 3, the pivot point A is made by means of a ball joint assembly between the bottom 4 of the bell 5 and an end wall 12 closing the top of the support structure 5, line junctions between the bottom 4 and the bottom wall 12 being provided by flexible connections such as 13, for example in annealed stainless steel.

Although the invention has been described in relation to particular embodiments, it is not limited thereby but is susceptible to modifications and variants that will be apparent to a person skilled in the art within the context of the claims below. Thus, as a variant of the embodiments of FIGS. 1 to 3, the tubular support may extend downwards, from the top of the outer envelope 2, in a shortened bell-shaped structure that is open upwards and extends downwards from the top of the inner envelope to a point situated above the center of gravity G. Also, in place of a tubular support 6 extending vertically into an equally vertical bell 5, the pivot point A may be formed between the upper generating line of a tubular support structure extending horizontally, between the domed ends facing the outer envelope 2, into a cylindrical hollow volume that is also horizontal formed in the inner envelope 1, between its axially opposed bowed ends, the latter representing in its turn a generally tubular configuration with a hollow volume that is off-center upwards. In this case, also, the connecting lines and conductors extend outwards from the pivot zone, into the horizontal tubular support, along the latter. 

1-8. (canceled)
 9. A cryogenic fluid tank, comprising an outer envelope and an inner envelope, the interspace between the envelopes being occupied by a multilayer insulating structure, wherein the inner envelope is supported on a pivot point (A) formed by a support structure secured to the outer envelope and extending inside the latter, the pivot point being situated above the center of gravity (G) of the inner envelope.
 10. The tank of claim 9, wherein the support structure extends inside a hollow volume of the inner envelope.
 11. The tank of claim 10, wherein it has lines for the transfer of fluids and/or electrical signals communicating with the inside of the inner envelope and extending outwards into the support structure.
 12. The tank of claim 9, wherein the inner envelope has a generally cylindrical configuration with a longitudinal axis.
 13. The tank of claim 12, wherein the support structure is orthogonal to the longitudinal axis.
 14. The tank of claim 10, wherein the hollow volume is formed by a bell-shaped structure extending transversely centrally inside the inner envelope.
 15. The tank of claim 9, wherein the pivot point is formed by a ball joint positioned between the walls of the hollow volume and the support structure.
 16. A use of the tank of claim 9 in a motor vehicle. 